Shawn and Gus investigate the death of Leonald Callahan, aka Diddle, a computer cryptologist who was the baritone in Gus’s old college a capella group.
Don and his team are out to protect former radical Benjamin Polk from a determined sniper who wants him dead, and who is leading the FBI on a cat-and-mouse chase as he closes in on his prey.
The body of a young war veteran is found in a parking garage and the murder is connected to a law professor who used to work for the Department of Justice.
Clark tells Jor-El he’s ready to start his training, but Jor-El sends him back to Metropolis to cut ties with Lois before he can begin. Chloe is shocked when Lois suddenly reappears after having been missing for weeks, but Lois has no recollection of vanishing into thin air with the Legion ring. Chloe begs Clark to use the Legion ring to go back in time to save Jimmy, but he refuses, driving a wedge into their friendship. Meanwhile, Zod arrives at the Luthor mansion...
A wave of terrorist bombs shuts down the city, pushing Team One to the limit and putting one of their own on the line.
Allison and her family deal with the outcome of her brain surgery and its possible lasting effects. Also, a local television station owner asks Devalos and Scanlon to look into the possible stalking of his sportscaster, who is also his wife.
It has been several months since Alpha's reign of terror and Echo, who is now randomly picking up flashes of past engagements, weds a British businessman who has ties to one of Ballard's open FBI cases. Topher becomes the target of Dr. Saunder's aggression after she finds out that she is actually a doll named Whiskey. Boyd takes on a risky venture and mixes business with pleasure, while DeWitt makes Ballard an irresistible offer.
The boys travel into the future to borrow a tool, but when their future sister Candace finds what they are up to, she realizes that she has the evidence she needs to travel back into the past to bust her brothers. When she returns to her own time, she realizes that she has made a terrible mistake that only she can fix.
Everyone is struggling after losing one of their own and are turning to any distraction they can find. Meredith and Derek seem to be consummating their marriage anywhere and everywhere, while Cristina and Owen have been instructed to abstain from sex by Dr. Wyatt.
A highway construction worker is the seventh in a series of mysterious disappearances in Lansdale, PA. The team come to investigate and finds traces of a mysterious paralytic. Meanwhile, Walter tries to send frogs to an alternate reality and Olivia realizes her recent trip has altered her in ways she can barely understand.
While Jeff looks to use a Spanish class assignment to get close to Britta, Pierce has something altogether different in mind.
The hospital staff is left to deal with the aftermath of George's passing. Hitting the staff hard, they all find unique ways to get through the various stages of grief. George's mom returns, faced with the difficult task of deciding what to do with his organs. Everyone is struggling after losing one of their own and are turning to any distraction they can find. Meredith and Derek seem to be consummating their marriage anywhere and everywhere, while Cristina and Owen have been instructed to abstain from sex by Dr. Wyatt.
Sam decides to stop hunting but has a hard time after he receives a surprise visit. Dean and Castiel try to find the Archangel Raphael in their bid to stop the Apocalypse.
Jane and Lisbon learn that the Red John case has been reassigned to a different CBI team led by the straight-shooting officer Sam Bosco.
As Elena tries to ignore Bonnie's warnings about Stefan, Tyler tries to embarrass Stefan by throwing a ball at him. However, his effortless catch and football skills impress everyone, leading Mr. Tanner to let him join the football team. Meanwhile, Elena invites Stefan and Bonnie to dinner in order to try to get the two to know each other, but the night ends up backfiring. Finally, the town is shocked by an act of violence.
When the world's population is given a glimpse of their future due to a mysterious global event, it forces everyone to come to grips with whether their destinies can be fulfilled or avoided.
Michael gets worried after a request from Jim, and Pam's busy with wedding planning. Darryl's worker's compensation claim makes Dwight suspicious.
While tending to the new community garden, Leslie and Tom discover someone has planted marijuana among the vegetables. In an effort to catch the people responsible, they pull an all-night stakeout. With Leslie's permission, Ann decides to go on a date with Mark.